1. Field of the Invention
This invention relates generally to a rack for mounting and connecting a plurality of electronics modules and, more particularly, to a rack for mounting and connecting a protected external module, which is coupled to a heat exchange unit.
2. Discussion of the Related Art
Many electronics systems employ independent electronic modules that are slideably positioned within an electronics rack, and electrically connected to each other therein. One particular known electronics rack is used for mounting and connecting avionics and electronics modules. As is well understood in the art, the operation of electronics systems generates heat. The closer the electronics modules are mounted together, the more heat is generated per unit volume, and the harder it is for the heat to dissipate. If too much heat is generated, the electronic modules may not operate amount of heat may create a fire hazard. Therefore, one of the primary focuses of the rack is to provide cooling of the modules.
In one rack design, cooling air is forced through a heat exchanger configured within the rack to provide cooling of the electronics modules. FIG. 1 is a perspective view of an electronics rack 10 of this type that is known in the art. The rack 10 includes an outer housing 12 having a front opening 14. A lower card guide 16 is mounted at a lower location within the housing 12 by flanges 18 secured to opposing side panels 20 and 22 of the housing 12. The card guide 16 is a single unit made of a heat conductive metal, such as aluminum. The card guide 16 includes a plurality of parallel tabs 28 extending from front to back that define a groove 30 there between each tab 28 includes an alignment nub 32 positioned proximate to the opening 14. An upper card guide (not shown) is also mounted within the housing 12 at an upper location in the same manner, and also includes parallel tabs defining grooves there between.
The parallel grooves 30 in the lower card guide 16 and the parallel grooves in the upper card guide are aligned and suitably spaced apart to receive internal electronics modules 36 in a certain configuration. Each internal electronics module 36 includes a lower rail 38 that is inserted in one of the grooves 30 in the lower guide 16 and the upper rail 40 that is inserted in the corresponding groove in the upper guide. When the internal electronics module 36 is slid into the housing 12, an electrical connector 42 is electrically connected with a meeting electrical connector (not shown) at the back of the housing 12 to provide the desired electrical connection. Multiple internal electronics modules 36 are slid into the housing 12 in a parallel format to provide the overall electrical system. It is generally desirable to set the spacing of the grooves 30 and thickness of the internal electronics modules 36 to allow as many modules as possible to be stored in the rack 10 to conserve space.
The internal electronics modules 36 generate heat during operation. The rack 10 therefore provides assisted cooling for the internal electronics module 36 to draw away the heat. FIG. 2 is a cross-sectional view of the rack 10-2 in FIG. 1. Rails 38 and 40 make contact with the lower card guide 16 and upper card guide in a heat transfer engagement. To provide the cooling, forced air is caused to circulate across the lower card guide 16 and upper card guide to draw heat away from the internal electronics modules 36. An inlet plenum 46 is attached to the side surface 20 at one side of the housing 12 and an outlet plenum 48 is attached to the surface 22 at an opposite side of the housing 12. Of course, the inlet and outlet plenums 46 and 48 can be reversed. The inlet plenum 46 includes a rectangular opening 50 through a back wall 52 of the housing 12 that allows cooling air to enter the plenum 46. The outlet plenum 48 includes a rectangular opening 54 through the wall 52 that allows the heated air to exit the outlet plenum 48 and the housing 12.
A heat exchanger 60 is positioned within a specially configured cavity and a base plate 62 between the bottom wall of the housing 12 and the card guide 16. A similar heat exchanger 63 is also provided between the top wall and the upper card guide. The heat exchangers 60, 63 include a plurality of spaced apart fins 64 that extend transversely to the opening 14. The cooling air from the inlet plenum 46 is forced into the heat exchangers 60, 63 and flows between the fins 64 across the card guide 16 to collect the heat therein. The fins 64 increase the surface area exposed to the cooling air and increase the heat removal capacity. As the operation of the internal electronics modules 36 heat the upper and lower card guides, air flowing between the fins 64 acts to draw heat away from the internal electronics modules 36 providing the cooling. The inlet plenum 46 provides cooling air to both the upper, lower and medial heat exchangers.
The spacing between the cooling fin 64 and the height and width of the cooling fin 64, is defined by the desired amount of air flow to provide the desired amount of cooling, as is understood in the art. In alternative variations, the rack 10 can include a plurality of stacked layers where internal electronics modules 36 are positioned between card guides and each separate layer, as disclosed, and cooling is provided at each layer in the manner as discussed herein.
The above described process of providing cooling of electronics modules in an electronics rack has been effective in removing heat from electronics modules. However, the overall electronics packaging density of the system and efficiency of the heat exchanger is reduced because only one side of the upper and lower heat exchangers 60, 63 is being utilized. Because the size and weight of the electronic system may be an important perimeter in different types of systems, it may be desirable to provide an electronics rack that allows for the mounting of a protected external electronic module which utilizes the exposed surfaces of two heat exchangers. It is therefore an object of the present invention to provide an electronics rack which is capable of accepting externally mounted electronics modules and efficiently takes advantage of the top heat exchanger arrangement.